It's not the pistons that "shatter", it's the RODs. Assuming you got deto that didn't snap the rods, then the piston RINGs would go first. The actual pistons themselves would be the last go to.

That being said, if you kept the detonation in check using good tuning and HIGH octane gas. Kept the EGTs under 1600F, the engine wouldn't break. A lot of people called BS when the first stock block Focus did 300whp stock internals, but when it was announced it was done on racing gas there were less doubts. Then, people were wondering how long the engine would last. It lasted around 3000mi before the owner decided to build up the engine and run 400+whp.

The Zetec is surprisingly robust, provided you keep Deto in check, using either good tuning, High Octane gas or both. Any deto over 150whp and the engine is toast.

2000 Rio Red I4 Cougar 200whp & 210wtq at 9psi 254whp & 276wtq with NX 35shot WRX TD04 Turbo, Cut Short Shifter, Strut Tower Bar, 17" ZN Wheels, Roush Springs, Starion Intercooler, NX 35 shot, HKS SS BOV, Full 3" exhaust,StreetFlight Chip